"Selection-dependent inputs are, in essence, a pretty simple concept: When someone initially makes a selection from one or more options in a form, they must provide additional input related to the selected option before submitting the form. The myriad solutions to this problem on the Web, however, indicate there’s more to this interaction than one might initially assume. The problem becomes particularly interesting when a form requires many additional inputs of varying types once a user makes a simple initial selection."
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